The terrible, sinking, feeling you get when something you worked very hard on is suddenly irreparably changed for the worst by the inconsiderate action(s) of an individual or small group.

Situational:
1. You spend all day working on that last minute assignment and after having completed it and left the room only breifly discover your pet dog/cat/parrot/liger has destroyed the fruits of your labour. This is all made worse by them trying to, in their own simple way, tell you that everything is fine.

2. The free from corporate interests social network for hospitality exchange I spent 5 years participating in just got sold out to the tune of 7.6 million without myself or the vast majority of 3 million members being consulted.

Conversational:
Person 1. 'What is wrong with you? You look sad.'
Person 2. 'I just got dumped by my partner. Completley out of the blue. They are seeing somebody else already. I feel pure fenton.'

Person 1. 'This shit is making me mad and fenton. I don't know if I should scream or puke. Maybe I'll do both.'
Person 2. 'Calm down dear. Everything is ok.'
Person 1. 'Fuck off! You did this to me!'

Horribe person (probably some kind of evil nemisis, but not a very bright one).
'I fentoned them all so hard they will be crying for a year while I count my illicit money. Muhahahaha. Muahahahaha. Hahahaha. Muhahahaha.'

An Irish last name. Fentons are rare now but are just the greatest of people. They're hilarious people that care so much about other people. They are strong and independent. Don't mistake their kindness for weakness though because once you do they will get their revenge on you.
Very attractive people, typically tall with golden hair and gorgeous eyes. Love laughing and working hard for what they deserve.

"Hey, there's Fenton"
"Dude we should invite him to the party tonight!"
"He's already invited"
"Oh yeah of course! haha can't wait!"

"Aye she's cute"
"Yeah man but that's Fenton's sister!"
"That's awesome dude!"
"Yeah it is but be careful. Break her heart and we'll never see you again man"